Expansible piston



July 20, 1937. JOHNSTON 2,087,761

EXPANS IBLE P1 STON Filed May 31, 1935 2 Sheets-Sheet l I] v 1 1; c Mot la/mceliJomstwg y 1937- c. s. JOHNSTON EXPANSIB'LE PISTON Filed May 31, 1935 2 Sheets-Sheet 2 Patented July 20, 1937 UNITED STATES PATENT OFFICE Claims.

This invention relates to expansible pistons and has for one of its principal objects the production of a simple and efflcient means for facilitating the expansion oi. the piston through the medium of hollow expansion pins, which pins will eliminate excessive weight and avoid overexpansion'at the top 01' the piston skirt under excessive heat.

Another object of this invention is the production of an expansible piston wherein the expansion pins are cast in the piston when the piston is die cast or molded.

A further object of this invention is the production of an expansible piston having expansion wedges or pins so mounted as to permit the full length of the piston skirt to be uniformly accurately adjusted to the fraction of one tenthousandth of an inch from top to bottom, due to the fact that the pins or wedges are cast in the piston at the time it is made, thereby insuring a perfect fit of the pins within the expansion sockets formed in the web of the piston.

A still further object of this invention is the production of an expansible piston wherein the expansion pins are located so as to prevent the piston pin bosses from being thrown out of alignment and the piston pins from being consequently clamped or tightened in the bosses as the expension pins are adjusted.

Another object of this invention is the production of a simple and efficient method of casting the expansion pins directly within the web at the 'same time the piston is being cast to insure of a proper fit of the expansion pins and thereby a1- low the full length of the piston skirt to be accurately adjusted. With these and other objects in view, this invention consists of certain novel constructions, combinations, and arrangements of parts as will be hereinafter more fully described and claimed.

In the drawings:-

Figure 1 is a side elevation of the piston showing the improved piston expander;

Figure 2-is a side elevation of the piston looking at right angles to Figure 1, certain parts being shown in vertical section;

Figure 3 is a horizontal sectional view taken on line 3-3 of Figure 1;

Figure 4 is a bottom plan view of the piston, certain parts being shown in section; 1

Figure 5 is a sectional view taken on line 5--5 of Figure 1;

Figure 6 is a group side elevation of one form of expansion pin;

Figure '7 is a similar view. of a modified form of expansion pin;

Figure 8 is a vertical sectional view through the mold or die showing the piston being cast;

Figure 9 is a sectional view taken on line 9-9 of Figure 8;

Figure 10 is a sectional view taken on line lit-I0 of Figure 8;

Figure 11 is a sectional view taken on line Il|l of Figure 8;

Figure 12 is a sectional view taken on line l2 -l2 of Figure 11.

By referring to the drawings, it will be seen' that P designates the piston which comprises a head and a depending skirt 2|, which skirt 2| is split, as at 22, and I9, to provide three sections thereby permitting the piston to contract under excessive heat.

The skirt 2| is provided with a cut-out portion 23 upon either side thereof through which the piston pin bosses 24 extend; These piston pin bosses 24 are molded or cast integrally with the diametrically extending web portions 25 which are integral with the skirt 2|, the web portions 25 being inset or set back within the sockets or cut-away portions 23 to place the piston bosses 24 wholly within the circumference of the skirt 2|, note particularly. Figure 3. The head 20 is connected to the bosses 24 by means of an integral depending web 25a as shown in Figure 1.

Each web portion 25 is provided with a pair of vertically extending spaced flanges 26 which provide a circular channel 21 located to one side of the piston pin boss, note particularly Figures 3 and 5.- These spaced flanges 26 provide along their outer edges a substantially V-shaped slot 260. which communicates with the channel 21. I preferably reinforce the web portions 25 adjacent the channels 21 in the respective web portions 25 bymeans of a metallic spring hinge plate 28 similar to the hinge plate disclosed in my previous application Serial Number 697,485,. filed November 10, 1933, relating to expansible pistons. These hinge plates 28 extend throughout the entire heighth of the web portions 25, the top and bottom ends of the plates 28 being flush with the upper and lower ends of the web portions 25. The vertically extending channel 21 in each instance tapers toward the bottom thereof and within this channel 21 is placed a hollow metallic tapering expansion pin 29, the pin 29 being open at its upper end, the lower or'narrow end being closed and terminating in an externally thread- -ed neck 30 upon which neck 30 is mounted the nut 3 I. This nut 3| abuts against the lower edge of the web, or to be more specific, the lower edges of the flanges 26, as will be noted particularly in Figures 1 and 5, thereby permitting the expansion pin 29 in each instance to be drawn downwardly by the rotation or adjustment of the nut 3|, in this way causing the piston skirt to be expanded as the tapering or wedge-like expansion pin 29 is drawn downwardly within the socket 21.

One of the important features of the present invention should be noted by considering Figure 3, wherein it will be observed that the expansion pins 29 carried by the respective web portions 26 are only placed upon one side or to one side of the piston pin bosses 24, in this way preventing the crowding of the piston pin bosses 24 or the twisting of the bosses out of alignment which action would cause the bosses to bind or'clamp upon the piston pins. By placing the expansion pins or wedges 29 only to one side of the piston pin bosses 24, the skirt 2| may be properly expanded without fear of throwing the bosses 24 out of alignment. The expansion pins 29 carried by the respective webs 25 are preferably arranged in transverse alignment upon similar sides of the bosses 24. This should be particularly noted by considering Figure 3.

From the foregoing description, it will be seen that the hollow expansion pins 29 have their upper ends open, and these open upper ends normally extend flush with the upper edge of the web portions 25 near the head of the piston, and these pins preferably extend substantially throughout the entire heighth of the web portions 25, thereby permitting the piston skirt to be uniformly and accurately adjusted to the fraction of approximately one one-thousandth of an inch from top to bottom, these pins 29 being cast in the slots at the time the piston is being cast, as will be hereinafter described, this method producing a perfect fit of the pins 29 within the expansion sockets 21. These hollow pins will also eliminate excessive weight and avoid over-expansion at the top of the piston skirt under excessive heat. By having the open end of the pin 29 in each in stance located near the head of the piston where the heat is more intense, and by using a hollow pin in place of a. solid structure, the hollow pin will absorb less heat and have a tendency to collapse or shrink a few thousandths of an inch thereby preventing the scoring of the piston cylinder under extreme heat. Because of this structure and in view of the above statement, it should be noted that the expansion pin 29 not only eliminates excessive weight but also avoids over-expansion at the top of the piston skirt when subjected to excessive heat.

Furthermore, it should be understood that the pins may be adjusted with positive accuracy due to the fact that the nuts 3| may be adjusted from the bottom and the tapering hollow pins extend substantially the full height of the web portion 25. Also by placing the pins only upon one side of the piston bosses 24, the cramping or tightening of the pins in the bosses is entirely eliminated. The piston designed and illustrated is particularly adapted for engines with V-type cylinder blocks or engines with horizontal cylinders. Furthermore, it should be understood that the expanding side of the piston is located so as to engage the bottom side of the cylinder wall to compensate for the additional wear caused by the weight of the piston and connecting rod.

A spring locking arm 32 engages each nut 3| for preventing the accidental loosening of the nut 3 I. This arm may be secured in any desired manner to the web 25 adjacent the boss 24, the arm 92 fitting in the groove 25b and socket 250 as shown in Figure 5. This spring locking arm is provided with a. depending end 32a. As a socket wrench is placed upon the nut 3| and contacts with' the end 32a the spring locking arm 32 will be pushed out of engagement with nut 3|. When the wrench is removed the arm will snap into locking engagement with the nut 3|.

In Figure 7, there is shown a modified type of expansion pin indicated by the numeral 33 having one vertical side 34, and one inclined side 35. This particular pin is especially designed for use in conjunction with cam 'or egg-shaped pistons, which type of piston is used in many of the larger engines. It should be understood that the pins, such as shown in Figures 6 and 7, may be tapered four ways, if desired, or tapered in any suitable manner to fit the desired type of piston without departing from the spirit of the invention.

As stated above, in carrying out this invention the expansion pins 29 are preferably cast in the web 25 which is preferably of aluminum, or to be more specific within the channel 21 while the web and channels 21 and flanges 26 are being die cast or molded. In this way, a more accurate fit will be obtained insuring a proper and satisfactory expansion of the skirt when the expansion pin is adjusted. The pins 29 are preferably dipped in plumbago or similar substance to prevent the same from adhering to the aluminum casting and the pins 29 may be loosened by driving the pins upwardly. It will be noted that due to the position of the spring hinge plate 28, the pins 29 will be cast in position under a spring tension, the pins 29 fitting flat against these spring hinge plates 28,- as shown in Figure 3.

I do not desire to limit myself to any particular type of die or mold, but a typical illustration is disclosed in Figures 8 to 12, inclusive. In this illustration it will be noted that the piston is indicated by the letter P which is formed within the sections 40 and 4|, constituting the mold, and a suitable central die 43 is inserted within the piston to properly shape the interior thereof, additional filler dies 44, 45, 46 and 41, being employed to produce the desired type of piston. The hinge plate 28 is cast directly in the web together with the expansion pin 29 in each instance and the pins 29 are so treated as to permit the movement of the pins 29 within the sockets 21 after the mold and dies have been removed. The dies 44 and 45 are provided with elongated ribs 48 which taper in cross section, thereby forming the V-shaped slots 29a when the piston P is being cast.

It should be understood that certain detail changes in the mechanical construction, combination and arrangement of parts may be employed without departing from the spirit of the invention, so long as such changes fall within the scope of the appended claims.

Having described the invention, what is claimed as new is:

1. A piston comprising a split skirt, a web supporting said skirt, said web having a tapering socket, a hollow expansion pin carried within said socket, said pin having a threaded inner end extending beyond said web. and a nut threaded upon said threaded end and abutting said web for adjusting said pin longitudinally to expand said skirt.

2. A piston of the class described comprising a split skirt, a web supporting said skirt, said web having a longitudinal socket, an expansion pin fitted in said socket, said expansion pin having a straight side and also an inclined side, and means abutting the ends of said web and engaging said expansion means for expanding and contracting said expansion means.

socket, said pin having a threaded inner end extending. beyond said web, a nut threaded upon said threaded end and abutting said web for adjusting said pin longitudinally to expand said skirt, and a locking device for said nut.

4. In combination with a piston having a split skirt, a web formed upon the inner wall of said skirt, said web having an expansion channel, an expansion pin adiustably mounted within said channel, a hinge member formed partly within said web and spanning the channel and constituting a closure for one side of the channel, the opposite side of the channel being longitudinally slotted and open tree to expand.

5. In combination with a piston having a split skirt, a web formed upon the inner wall of said skirt, said web having an expansion channel, an

expansion pin adjustably mounted within said channel, a spring hinge member abutting said expansion pin and formed partly within said web and spanning the channel and constituting a closure for one side of the channel, the opposite side of the channel being longitudinally slotted and open.

CLARENCE S. JOHNSTON. 

